The targeting vector was designed to insert an expression optimized iBE reporter construct downstream of the Col1a1 locus. The construct contains a tetO promoter, an optimized BE3RA and rabbit beta globin polyA (RBGpA) sequence. BE3RA contains a rat APOBEC cytidine deaminase at the N-terminus of inactive dCas9 (Cas9-D10A) and a uracil glycosylase inhibitor (UGI) domain at the C-terminus. (J:337058)